Hot dimpling tool and control means therefor



Sept. 16, 1958 J. R. GUNTHER HOT DIMPLING TOOL AND CONTROL MEANS THEREFOR Fil ed Aug. 11, 1953 X [EMU/7E2 IN V EN T OR. Jam 2 60/1 7752 rr y va proper degree of heat-head from the male die.

' 2,852,060 Patented Sept. 16,1958

HOT DIMPLING TOOL AND CONTROL MEANS THEREFOR Joseph R. Gunther, Inglewood, Calif., assignor to lgoufglas Aircraft Company, Inc., Santa Monica,

all 7 Application August 11, 1953, Serial No. 373,593

7 Claims. (Cl. 15321) ing tool itself in other hot-metal working operations than those involved in hot dimpling. For example, it will be- .come apparent that the principles of the invention may also be employed in hot-forging sheet metal and in hot drawing and hot extruding bar metal.

In contemporaneoushot-dimpling apparatus, the temperature and dwell period actually employed in heating the sheet around the rivet hole to be dimpled depend entirely upon the judgment and patience of the operator. As a consequence the sheet-metal can well be, and often is, either underheated or overheated. One of the results of underheating is that when the forging die strikes the cold sheet, the latter may crack or otherwise fail strengthwise around the rivet hole. The results of overheating are obvious, and in the case of heaters employing high current density are almost inescapable when any of the contemporary manual control devices are employed.

The present trend in the sheet-metal fabricating industry is towards larger heavier rivets and larger dimple holes so that the forging stroke in dimpling the rivet holes requires all the air pressure that can be developed inthe pneumatically operated dimpling machine to be applied to the dimpling die. However, contemporary control systems eifect exhaust by means of a bleeder hole in the pressure line to the squeezer, gun or other metal-forming tool. Such exhaust means reduce the pressure of the air that acts on the dimpling die by as much as 40 pounds per square inch.

Moreover, in many hot dimplers although the squeezeroperating air lines may be leaky and therefore incapable of transmitting the full amount of the source pressure to the dimpling die, nonetheless the control apparatus operates at even this low pressure. It applies the dies or other metal working instrumentalities to the work at an insufliciently large pre-pressure to enable the sheet to receive As a consequence, the sheet is underheated with the results mentioned hereinabove.

Many states have labor laws prohibiting women employees from lifting articles weighing over 25 pounds. Inasmuch as most hot dimpling control panels weigh well :over this limit, the women find it necessary to .call for a the dies-to thesheet-material; (2) the degree ofheatapplied to the die or dies contacting the sheet so as to pres vent overheating and obviate underheating, and (3) the dwell-time on the sheet of the heated die or dies. When a preset timer connected to the heating circuit times out, it opens the heating circuit to prevent scorching of the sheet material. Thus, the heating is no longer dependent upon the operators judgment.

The sheet-material should not be worked until it has reached a predetermined optimum temperature around the rivet-hole to be dimpled. For Dural sheet-material, this temperature is of the order of 350 F. and to produce this sheet-temperature, the female die must be elevated to a temperature of the order of 650 F. If Dural is dimpled at temperatures much different from these, it will cold-crack radially and-circumferentially of thedimple.

By virtue of the present means, the pneumatic system cannot be actuated to operate the,metal-working tools until the pyrometer in the panel indicates that the heated die is up to the optimum temperature.

The panel obviates the previous continuous bleeding from the pressure air line to the metal-working tool and incorporates the step of automatically exhausting the fluid from the tool at the end of each cycle. This exhaust functions only intermittently instead of continuously and is so configured with the means in the panel for applying pre-pressure that the previous oscillating malfunctioning of the air supply in the pro-pressure is eliminated. .Gen-

erally to this end the invention provides atwo-valve closed circuit for the pressure fluid which releases the metal working tool and exhausts air from the circuitevery time a pre-set timer adapted for also controlling the other operations, completes its timing function.

The Working fluid can be applied to the metal-working tool in the pre-pressure phase of the operations only when all the air lines are airtight and leakproof so that only the full pressure-value developed at the pressure source can be applied to the metal-working tools. Thus, the pro-pressure applied to the sheet material by the dies in the allotted short period of timeof thepre-pressure phase will enable the sheet to be raised to the optimum working temperature in this period of time elapsing before the forging stroke of the machine.

Despite the incorporation into the panel itself of almost the entirety of the electrical components of the invention and of similar incorporation of a large proportion therein of the pneumatic system components, the article of the present invention is more compact job for job and capacity for capacity than subsistent such articles and occupies a lesser volume of critical space in thearea than contemporary hot dimpling control panels. By the same token, the weight of the article is so much reduced below the critical limit of 25 pounds that no male assistance in transferring the article from station to station is required by women operators.

A number of other advantages and advances are inherent in the device of the present invention and these features will either be made manifest hereinafter or become apparent from a perusal of the disclosure herein.

In order to further elucidate the invention, one of the many design-forms it is at present contemplated that the invention may assume is, by way of example only, illustrated in the accompanying drawings thereof and described in detail hereinafter in conjunction withthese drawings.

In said drawings:

Figure 1 is a view, partly sectional and partly frag mentary, of a hot-dimpling machine provided with a control system of the present invention; and

Figure 2 is a perspective view of the present control panel, orbox, that contains the electrical and pneumatic control means illustrated in Figure 1.

The embodiment illustrated broadly comprehends a control panel unit, or box, A, Figure 2, containing the electrical and pneumatic control circuitry B and C of Figure 1, the electrical circuitry being connectible to the hot-dimpling machine D by a cable-conductor terminating at the one end in the machine; and at the opposite end in the pin member E of a Cannon plug, the socket member F of which is carried by the box.

Certain manipulatable members and essential condition-indicators are carried on the face of the box and these include a first timer having a selectingly settable time-switch handle G movable over an associated dial; and a second timer having a similar switch handle H and associated dial. The face of the box also carries the dial K of a pyrometer operatively associated with the female die, as'later particularized; a main-line circuit closing switch 19; a toggle switch L manipulatable to control the degrees to which the male die is heated before heating energy is cut off from the female die so as to regulate the temperature to which the sheet is raised in accordance with the nature of the alloy composing the sheet material; an air-pressure gauge 8, and a pre-pressure regulator 9.

The electrical means associated with the panel A, the hot dimpler D, and the pressure-air actuating means C for the dimpler comprise a heater circuit, a heating-control circuit, a die-temperature signalling circuit, a timerscircuit to the solenoids of the valves controlling the application of pressure-air, the below working-temperature lock-out circuit, the thermo-couple broken circuit which protects the sheet-material from burning it thermocouple control is lost; and the circuitry for conditioning the system for working either on Dural sheet-material or titanium-alloy sheet material.

First describing the circuitry and configuration provided for activating the heater, electrical energy is applied from the pole of the A. C. source through a conductor 11 to the electric resistance heater 12 of the hot dimpler D thereby to raise the temperature of the heater. Therefrom, energy returns via conductor 13 to contact 14, normally abutted by movable contact 15 (when coil 32, later described, is not passing energy). From contact 15 energy passes through conductor 16 to the common cold terminal 16A of the A. C. source.

Thus, the heater 12 is activated and de-activated by the closing and opening of the contacts 14 and 15 under the action of the heater-control circuit that includes the coil 32 and is hereinafter particularized. The heater-control circuit itself is in turn controlled by the temperature signal circuit that includes the thermocouple 17 and the pyrometer 18 as hereinafter described.

The upper portion of the conductor 11 may include a handswitch 19 and a fuse 21 and the lower portion of the conductor 11 energizes the primary 23 of an isolation transformer that includes a core 25 and a secondary 24, the transformer constituting the first part of the heater control circuit. Alternating energy, or A. C., is applied from the secondary 24 through conductors 26 and 27 to the rectifier 28 where it is translated into D. C., and, for a purpose later discussed, passes to a microswitch pulse unit 29, resistor 31, coil 32 of a relay 33, through conductor 34 to a contact 35 in the pyrometer. Member 35 contacts an auxiliary needle 36' in the pyrometer when the signal generated by the temperature control thermocouple, later described and passed to common coil 37 of the pyrometer is sufiiciently large to move the main needle 38 of the pyrometer upscale sufficiently to make member 36 contact with 35. Energy then passes from needle 36 through a coil 39 in the pyrometer to the common terminal 41 of the pyrometer electrical input means. Thence it passes through conductor 42 back into transformer-secondary 24.

In accomplishing this circuit-the heater-control circult-the A. C. current passing from the secondary 24 through the conductors 26 and 27 is rectified in 28 to a D. C. current and then smoothed through a filteringtype condenser 44. The output of the latter is employed to energize the microswitch type pulse unit 29 which is mechanically opened and closed periodically, as later described, by an interrupter motor 108, including a shaft and cams, not shown, in order to periodically interrupt the flow of current through the heater-control circuit so as to de-energize coil 39, thus in turn enabling contacts 35 and 36 to open. Contacts 35 and 36 are normally in an open position. This action allows the main needle 38 of the pyrometer to move downscale if the signal across pyrometer common coil 37 from the thermocouple has diminished.

Now if contacts 35 and 36 are maintained open, capacitor 47 eventually discharges, and since there is then no current flow through coil 32, points 14 and 15 are in contact and energize heater 12 as described hereinabove.

The die-temperature signalling circuit, or thermocouple normal circuit, includes a thermocouple 17 which senses the heat in a female die 49 which is imparted thereto by the heater 12 and activates means which control the temperature of die 49. To this end, the current generated in 17 by the die temperature passes through conductor 51 through coil 37 to the common terminal 41 of the pyrometer and returns to the thermocouple 17 via conductor 52. By thus passing through coil 37, a righthand torque is imparted to the needle 38 in proportion to the amount of energy derived from the thermocouple. Since the pyrometer is of the DArsonval galvanometer type, this right-hand torque is opposed by a hairspring, not shown but attached to needle 38 and this hairspring tends to impart a left-hand torque to this needle for a purpose later described. The contacts 35 and 35A may be set on the pyrometers calibrated dial 53 to effect this control of the heater at any desired temperature.

The timed circuitry for operating the solenoids 54 and 55 of the valves 56 and 57 for controlling the application of pre-pressure and forging pressure compressed air to the dimpling machine includes means arranged to be energized by the A. C. source 1015 and controlled by the thermocouple 17 and by the die-temperature signalling circuit already described, and,- in case the thermocouple is inoperative, as sometimes may occur, by circuitry and means, hereinafter described, for looking out the heater circuitry or the air-pressure applying circuitry.

In the first phase of the operation of the timed circuitry for operating the solenoids of these valves, energy passes from the hot pole 10 of the A. C. source through the then-closed, hand-operated trigger 58 of the dimpling machine (here shown as of the squeezer type) and through a conductor 59. If the signal put on the coil 37 from the thermocouple is sufficiently large to open the pyrometers left-hand contacts 35A and 36A, then the contacts 61 and 62 will be in closed condition as described hereinabove. Thus, current will pass through conductor 59 into conductor 63, through the solenoid of valve 55, through conductors 6'4 and 65 through terminal S of timer P, to terminal R thereof. From terminal R current passes through conductors 66, 67, and 68 back to the cold pole of the A. C. source.

This energization-sequence opens and establishes the pre-pressure air flow to the dimpler. In the present examplificatory embodiment of the invention, this controlled pressure is of the relatively low order of 1080 p. s. i. and its circuit passes from the compresed-air inlet, through the regulator 9, air-pressure gauge 8, and check valve 9A into 3-way solenoid-valve 55. Thence it passes through outlet 69 and air-hose 71 to the dimpler. It will be readily comprehended by those skilled in the art of pneumatically operated dimpling machines that the outlet member 69 connected to hose 71 is a conventional fitting of the type that includes a standard unilateral-flow restrictor means therein. Such one-way restrictor means, as is well known, open to permit fluid-flow into the member 69 from valve 57 only when such fluid is at or above predetermined minimum pressure, here preferably of the order of p. s. i. Thereby the male die 72 is advanced and urges the sheet to be dimpled against the female die with the predetermined pre-pressure as set by the regulator valve 9. This pre-pressure is thus rendered suflicient to enable the heated female die to raise the workpiece to the optimum dimpling temperature before the forging action occurs as described hereinafter.

It will be observed that the pre-pressure air cannot be applied to the male die if there is a leak in the pneumatic system which would preclude the application of the full value of the pre-pressure force of 10-80 p. s. -i.

It should be noted that the predetermined time requisite to heat a particular sheet .of a given thickness and alloy composition is first set on timer N by handle G. The latter, when the pre-set time has elapsed, will trigger off the high-pressure air circuit for applying the forging, or final forming, stroke to the male die, as hereinafter particularized.

contemporaneously with the closing of the manually closed trigger 58, current also flows from contact 62 through conductor 73 to terminal 74 activating timer N. This current is divided and also passes through conductor 75 to terminal 76 which is open to terminal 77 until the time-interval pre-set on timer N has elapsed at which time 76 becomes connected internally to '77, causing current to flow from 76 through 77 to conductor 78 and terminal 79 of timer P actuating timer P. Current also flows through conductor 81 into the solenoid of valve 56 causing it to open and admit the high pressure air of the pneumatic system-usually of the order of 100 p. s. i. -into hose 71 and thence to the dimpler. This highpressure air effects the final metal working action in the form of a powerful forging stroke exerted by the squeeze dies.

Timer P opens the common circuit or energy-path to solenoid valves 56 and 57 when the predetermined time set on timer P has elapsed, thus closing off both the high pressure air circuit and the low pressure air circuit. With no pressure air now passing through hose 71, the plunger of the dimpler releases in the known manner and the male die automatically retracts, thereby ending the dimpling c cle.

The common circuit mentioned above in connection with the control of the application of pressure-air is that electronic circuit, which, tracing energy flow from negative to positive in the electronic manner, begins at cold pole 16A of the A. C. source, passes through conductor 67 to the uppermost terminal 82 of timer N dividing through conductors 83, 66 and 84 and into terminal Q of timer P, dividing also through conductor 85 and passing to terminal R of timer F. From R, current passes to terminal S, thence through conductors 65 and 64 to 2-way solenoid valve 56. From the junction shown the circuit divides to solenoid 55 to provide a current-path for the solenoid of valve 57.

The circuitry for locking-out operation of the squeezer when the sheet-material is below optimum temperature so as to obviate chattering and arcing. Current through relay coil 89 causes the contacts 61 and 62 to be pulled away from eachother, opening the trigger-and-solenoids circuit so that it and the solenoid-valves will not, when the system is in this condition, operate at all.

- In this subdivisional circuitry current flowing through pulser 93 is periodically broken, so as to de-energize coil 37 thereby to momentarily remove the left-hand torque from the needle 38. Hence, the right-hand torque producing signal on coil 39 is enabled to open points 36A and 35A which allows the contacts of the left-hand relay to be closed by virtue of de-energization of coil 89.

The circuitry and means for preventing burning of the sheet-material when and if the thermocouple or any of its circuitry are broken and can no longer exert its control function on the heater-circuitry comprises means for sensing the negative potential then existing at point Y on conductor 99 and directing it through conductor 101, limiting resistor 102, conductor 163, variable resistor or adjustabie linear potentiometer 104, conductor 105, closed switch 167 and through the conductor shown into common coil 37 of the pyrometer and thence to the secondary 24, which is the source of this potential difference.

However, the current passing through coil 37 can create a voltage drop only if the aforedescribed thermocouple circuit is open. For, if this thermocouple circuit is intact, the resistance therein is suificient to nullify the voltage in coil 37 because of the high resistance ratio between the thermocouple circuit, designedly of relatively low resistance, and the pyrometer, intentionally of relatively high resistance.

Now, when the thermocouple circuit is in the aforesaid open condition, the voltage built up as aforedescribed across coil 37 causes needle 33 to move up its scale and it eventually closes points 35 and 36 thereby shutting off the heater 12 as, and for the purposes aforedescribed.

The seventh and last one of the interrelated but distinct subdivisional circuits of the present controlsystem is provided for changing the control-conditions from those adapted for the hot-dimpling of Dural sheet material to those adapted for the hot-dimpling of titanium-alloy sheet-material. To these ends, voltage produced by the thermocouple 17 causes a current to fiow through conductor 51 to switch L. When the latter switch is closed, the control system is set up for work on Dural sheet material; and when the switch L is open, the system is set up for work on titanium alloy sheetmaterial.

or when the thermocouple is broken is so arranged and fed that it passes D. C. current, if the signal across coil 37 is of a low value, through conductor 52 to the common point 41 of the pyrometer and thence through coil 37, thus enabling left-hand contacts 36A and 35A to close. Current thus continues on from coil 37 through points 36A and 35A, conductor 86, coil 89, conductor 91, resistor 92 and left-hand microswitch pulser 93, which is also mechanically connected to the interrupter motor for periodic make-andbreak actuation. From pulser 93 current passes through conductors 94 and 95, rectifier 96, conductor 97, resistor 98 and back to secondary 24 of the transformer.

In so passing, the current traversing coil 37 imparts to the needle 38, left-hand torque which is additional to that imparted by the conventional hairspring mentioned above as also acting on the needle 38 thereby causing needle 38 to forcefully press point 36A against point 35A When switch L is closed, a resistor 106 provided therein is shunted out and the resistance of the thermocouple circuit is rendered low so as to pass a comparatively weak signal to move the needle 38 upscale against its stop.

If switch L is open, current passes directly through resistor 106, setting up a higher total, or overall, resistance in the thermocouple circuit. The latter then necessitates the employment of a comparatively larger signal in order to upscale the needle 38 against its stop. Current then passes through conductor and coil 37 and returns to the thermocouple through conductor 52.

It can now be perceived that in effecting hot dimpling of a Dural sheet by means of a pneumatically operated, electricaly heated squeeze type dimpler of the nature indicated at D, the switch L being closed, for operations on Dural, the operator sets the pie-pressure regulator to read from 10-80 p. s. i., the timers N and P are set by handles G and H to the optimum dwell periods and the main-line switch 19 is then closed.

Energization of the circuits described hereinabove are thereby set in train, the first resultant being the squeezing together of the dies against the Dural sheet at the pre-pressure of 10-80 p. s. i. These dies are, by the timed, pneumatic system controlling circuitry iaforedescribed, maintained together against the sheet long enough at this pressure to raise the sheet to a preferred temperature of 350 F., the heater 12 having been, for this purpose, automatically raised by the circuitry aforedescribed in connection with group A, to a temperature of the order of 650 F. thereby raising the female die to the same high temperature.

When the pyrometer indicates this temperature of 650 F. at the female die, the die will be held at this temperature for a predetermined dwell-period at the end of which the control means and circuitry described above will trigger the forging-stroke of the male die.

Pressure air will then exhaust through port 120 and the aforedescribed cycle will re-commence.

It will be recollected that the forging stroke of the squeezer cannot be triggered until the pyrometer indicates, via the thermocouple, that the heated-female die has reached 650 F. in contact long enough with the Dural sheet to have, presumably, raised the latter to the optimum working temperature of 350 F.

If the heat in the female die exceeds the optimum amounts, the main needle of the pyrometer will be upscaled until the contacts 35 and 36 close, thus automatically shutting off the heater as aforedescribed.

lrVhen the sheet material is below optimum temperature or when the thermocouple is broken, the trigger and solenoids valves circuitry are broken as described above, so that the dimpler cannot operate on the sheetmaterial.

If the thermocouple is broken or inoperative, the present control system prevents the heater continuing on, out of control, to heat the sheet, as described hereinabove.

When, instead of Dural, a titanium alloy sheet material is being dimpled, the switch L is shifted to open as indicated and the control system operates as aforedescribed to pass more heat generating current through the heater 12 and the titanium alloy sheet.

Although the metal-working operation has been described, by way of example, as a hot-dimpling squeeze and forge operation, it is manifest that the control system of the invention can equally well be employed in connection with other hot metal-working operations. Also, although certain standard electrical instrumentalities have been configured according to the present principles of control, it is obvious that other equivalent electrical devices may be employed.

Accordingly, it is to be understood that the specific embodiment herein disclosed by no means constitutes the sole form which the invention may take and that the synthesis of the invention is limited only by the scope of the sub-joined claims.

I claim:

1. Control means for an electrical resistance type heater operatively associated with a pneumatically operated metal-working instrumentality, comprising: a source of electrical energy; an electrical-resistance type heater arranged and adapted to heat a metal-working instrumentality; conductor paths operatively connecting said source and said heater in circuit; electrical temperatureindicating means; a thermocouple operatively associated with said metal-working instrumentality so as to sense and translate the heat content thereof; conductor paths operatively connecting said thermocouple to said temperature-indicating means; a relay operatively interposed in the circuit between said source and said heating means; an upper-limit electrical contact on said indicating means; conductor means operatively connecting said limit-contact to said relay; a complementary movable contact in said indicating means operatively electrically connected to said thermocouple; and means in said indicating means for displacing said complementary contact towards said upper limit contact under current flow from said thermocouple; a complementary and movable metal-working instrumentality; a pressure-fluid operated piston-andcylinder adapted to operate said complementary instrumentality towards the first-said instrumentality; pressurefluid supplying means operatively associated with said piston-and-cylinder; electrically-operated fluid-flow controlling means disposed in said supplying means and operatively connected to said electrical source; and means for preventing flow-establishing operation of said flow-controlling means unless the temperature of said metalworking instrumentality is indicated at a predetermined value on said indicating-means.

2. Control means for an electrical resistance type heater operatively associated with a pneumatically operated metal-working instrumentality, comprising: a source of electrical energy; an electrical-resistance type heater arranged and adapted to heat a metal-working instrumentality; conductor paths operatively connecting said source and said heater in circuit; electrical temperatureindicating means; a thermocouple operatively associated with said metal-working instrumentality so as to sense and translate the heat content thereof; conductor paths operatively connecting said thermocouple to said temperature-indicating means; a relay operatively interposed in the circuit between said source and said heating means; an upper limit electrical contact on said indicating means; conductor means operatively connecting said limit-contact to said relay; a complementary movable contact in said indicating means operatively electrically connected to said thermocouple; and means in said indicating means for displacing said complementary contact towards said upper limit contact under current flow from said thermocouple; a' complementary and movable metal-working instrumentality; a pressure-fluid operated pistonandcylinder adapted to operate said complementary instrumentality towards the first-said instrumentality; pressurefiuid supplying means operatively associated with said piston-and-cylinder; electrically-operated fluid-flow controlling means disposed in said supplying means and operatively connected to said electrical source; and means for preventing flow-establishing operation of said flowcontrolling means unless the temperature of said metalworking instrumentality is indicated at a predetermined value on said indicating means; said indicating means including a DArsonval galvanometer including a common coil electrically connected to said source, and a laterally lovable main needle of conductive material, the common coil carrying said needle; a pair of electrically conductive laterally movable auxiliary needles; a control circuit for the pneumatic system for operating said metal-working instrumentality terminating adjacent the opposite lateral limit-position of said needles, said control circuits being adapted to be actuated on contact of the respective terminals by the respective needles; and means operatively connected to said needles and operatively responsive to thermal limit conditions in said metal-working instrumentality so as to laterally move said needles and effect said respective control-effecting contacts with said terminal portions.

3. Control means according to claim 1 in which the operating means of the indicating means includes a DArsonval galvanometer having a common coil and a main, conductive needle carried by said coil for lateral movement toward an upper limit; and in which control means there are heater cut ofi means terminating near said needle, the one of said conductor paths that connects said thermocouple to said common coil in said indicating means including variable resistance means of the linear, adjustable potentiometer type operatively interposed in said one of said conductor paths whereby current passing through said common coil can build up a voltage difference therein only if the thermocouple circuit is open, so as to then upscale said main needle into contact with said heater cut off means.

4. Control means as recited in claim 1, in which said indicating means includes a DArsonval galvanometer having a common coil electrically connected to said thermocouple; a laterally movable main needle operatively carried by said common coil; a secondary coil; a pair of auxiliary needles operatively carried by said secondary coil; an isolation transformer energized by said source and adapted to protect said galvanometer; conductor paths extending from the secondary of said transformer; a rectifier in the lead one of said conductor paths; a pulser fed by said rectifier; a relay connected to said pulser for operation by the output of said pulser; a conductor path terminating operatively adjacent the one of said auxiliary needles and adapted to be contacted thereby to close the circuit through said secondary coil; and a return from said torque coil to the secondary of said transformer.

5. Control means as recited in claim 1, in which said indicating means includes a DArsonval galvanometer having a common coil electrically connected to said thermocouple; a laterally movable main needle operatively carried by said common coil; a torque coil and a pair of conductive auxiliary needles operatively carried by said torque coil and adapted to operate a circuit for controlling said pneumatic means having a terminus near said auxiliary needles, the one of said needles being carried by the other and lying nearer said terminus; and said control means including an isolation transformer for protecting said galvanometer and energized by said source; a conductor path extending from the secondary of said transformer; an A. C.D. C. rectifier operatively interposed in said path; a microswitch-type electrical pulser electrically connected to the output of said rectifier; a relay electrically connected to the output of said pulser; and a conductor extending from said relay into operative adjacency with said carried needle and adapted to be contacted thereby so as to operate said circuit for controlling said pneumatic means.

6. In a control means of the type described for use with a metal-working instrumentality and including a thermocouple; an electrical resistance heater adapted to be controlled by said thermocouple; and an independent source of electrical energy: a pyrometer for translating the electrical energy transmitted to it from said thermocouple into indications of the temperature of said metalworking instrumentality, and comprising a temperature scale; a DArsonval galvanometer including a main needle; a common coil connected electrically to said thermocouple and said coil being supported by said needle and adapted to torque it clockwise and sweep it over said temperature scale; a pair of laterally spaced mutually united conductive auxiliary needles; an oppositely Wound torque coil operatively connected to said source and supported by said auxiliary needles and adapted to torque them counter-clockwise over said scale; and a controlcircuit terminal disposed operatively adjacent each of the lateral limits of movement of said needles, the one of said terminals forming part of a control circuit for said heater.

7. In a control system for apparatus of the nature described and including a source of electrical energy and a source of pneumatic pressure fluid: pneumatic motive means; a pneumatic conduit system extending from said pressure-fluid source to said motive means; and electrical circuit including said source of electrical energy; a triggerswitch interposed in said circuit; a solenoid operated three-way valve having its solenoid operatively connected in said circuit, the valve-portion of said solenoid operated three-way valve being operatively interposed in said pneumatic conduit system and said valve-portion being outlet-flow communicated with said motive means; a first electrical timer; a conductor path connecting said solenoid and said timer; a reducer valve operatively interposed in said pneumatic system anterior to said three-way valve; a solenoid operated two-way valve operatively interposed in said pneumatic system onwardly of said three-way valve said two-way valve being outlet-flow communicated with said motive means, said three and two-way valves being mutually interconnected to form parallel flow paths; an electrical conductor path connecting the-solenoid of the two-way valve to said first timer; a second timer; a conductor path connecting the two timers; another conductor path connecting the two timers and connecting the second timer to the solenoid of the two-way valve; a conductor path connecting the first-said conductor path and the second-said timer; and a return conductor path extending from the second timer to said electrical energy source.

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